internet: allow peeking wrong IPv{4,6} headers (returns a zero deserialized size)

src/internet/model/ipv4-header.cc

@@ -341,8 +341,8 @@ Ipv4Header::Print (std::ostream &os) const
     {
       flags = "none";
     }
-  else if (m_flags & MORE_FRAGMENTS &&
-           m_flags & DONT_FRAGMENT)
+  else if ((m_flags & MORE_FRAGMENTS) &&
+           (m_flags & DONT_FRAGMENT))
     {
       flags = "MF|DF";
     }
@@ -424,10 +424,17 @@ Ipv4Header::Deserialize (Buffer::Iterator start)
 {
   NS_LOG_FUNCTION (this << &start);
   Buffer::Iterator i = start;
+
   uint8_t verIhl = i.ReadU8 ();
   uint8_t ihl = verIhl & 0x0f; 
   uint16_t headerSize = ihl * 4;
-  NS_ASSERT ((verIhl >> 4) == 4);
+
+  if ((verIhl >> 4) != 4)
+    {
+      NS_LOG_WARN ("Trying to decode a non-IPv4 header, refusing to do it.");
+      return 0;
+    }
+
   m_tos = i.ReadU8 ();
   uint16_t size = i.ReadNtohU16 ();
   m_payloadSize = size - headerSize;

src/internet/model/ipv6-header.cc

@@ -32,8 +32,7 @@ NS_LOG_COMPONENT_DEFINE ("Ipv6Header");
 NS_OBJECT_ENSURE_REGISTERED (Ipv6Header);
 
 Ipv6Header::Ipv6Header ()
-  : m_version (6),
-    m_trafficClass (0),
+  : m_trafficClass (0),
     m_flowLabel (1),
     m_payloadLength (0),
     m_nextHeader (0),
@@ -130,8 +129,7 @@ TypeId Ipv6Header::GetInstanceTypeId (void) const
 
 void Ipv6Header::Print (std::ostream& os) const
 {
-  os << "("
-  "Version " << m_version << " "
+  os << "(Version 6 "
      << "Traffic class 0x" << std::hex << m_trafficClass << std::dec << " "
      << "Flow Label 0x" << std::hex << m_flowLabel << std::dec << " "
      << "Payload Length " << m_payloadLength << " "
@@ -168,9 +166,11 @@ uint32_t Ipv6Header::Deserialize (Buffer::Iterator start)
   uint32_t vTcFl = 0;
 
   vTcFl = i.ReadNtohU32 ();
-  m_version = vTcFl >> 28;
-
-  NS_ASSERT ((m_version) == 6);
+  if ((vTcFl >> 28) != 6)
+    {
+      NS_LOG_WARN ("Trying to decode a non-IPv6 header, refusing to do it.");
+      return 0;
+    }
 
   m_trafficClass = (uint8_t)((vTcFl >> 20) & 0x000000ff);
   m_flowLabel = vTcFl & 0xfff00000;

src/internet/model/ipv6-header.h

@@ -184,10 +184,6 @@ public:
   virtual uint32_t Deserialize (Buffer::Iterator start);
 
 private:
-  /**
-   * \brief The version (always equal to 6).
-   */
-  uint32_t m_version : 4;
   /**
    * \brief The traffic class.
    */